Piano



United States Patent 2,836,093 PIANO Herbert 0. Crippen, Sr., Chicago, Ill. Application September 15, 1954, Serial No. 456,134

Claims. c1. 84-196) This invention relates to improvements in pianos.

The principal objects of the present invention are to provide in a piano, improved details of construction to cause the sound board to be more responsive to the vibrations of the piano strings to the end that the sound producing vibrations of the strings will be more completely and more accurately reproduced and amplified by the sound board; to provide an improved resonating chamber arrangement which will aid in improving the tone and also the volume of the piano; and other objects and advantages of the invention will be understood by reference to the following specification and accompanying drawing wherein the invention is represented in a preferred form.

In the drawing:

Figure l is a perspective illustration of the back of an upright piano embodying the invention, certain parts being broken away to more clearly illustrate details; and

Figure 2 is a cross-section on a horizontal plane represented by the line 2-2 of Figure l.

The improved piano construction represented in the drawing comprises a more or less conventional case 1 in which a soundboard 2 is mounted in the usual manner. As is usual, the sound board 2 is crowned, that is it is arched forwardly, i. e., toward the front of the piano. Strings, one of which is represented at 3, are stretched between supports on a suitable plate or frame (not shown) usually made of metal and of sufficient rigidity to withstand the forces applied thereto by the strings which which are normally placed under high tension, of the order of one hundred sixty-eight pounds. These strings bear on treble and bass bridges 4 and 5 respectively, said bridges being suitably secured to the front of the sound board. The strings bear with considerable back pressure on the bridges d and and tend to flatten the sound board.

In conventional piano construction, the back of the sound board is provided with a series of braces or ribs 6 which heretofore have been considered necessary, primarily for the purpose of counteracting the back pressure of the strings which tends to reduce and destroy the crown in sound board. According to the present invention, the ribs e, if employed at all, may be fewer in number, that is, they may be spaced farther apart, and they may be made of lighter cross-section since they are not relied upon for supporting the crown or curvature of the sound board. The ribs maybe wholly omitted so far as support of the sound board crown is concerned, but they may be employed if desired for certain purposes, for example, as a convenient means for securing together sections of a sound board when the sound board is made of two or more sections assembled edge to edge.

For improving the tone quality of the piano, and also, to preserve the crown in the sound board, bridge back pressure support-tone bars such as indicated at 7 are positioned between the sound board 2 and the rear posts 8 or other sturdy parts of the back structure of the piano frame or case, said back structure being spaced rearwardly ree from the sound board substantially as shown in Figure 2. These posts 8 are present in practically all upright pianos and they are normally very sturdy or stout posts as indicated in the drawing so that they are-well able to resist the pressure of the strings.

The pressure exerted by the strings against the bridges and sound board and by the sound board against the support-tone bars 7 is very high and I have found that when the bars 7 are made of a length to fit very tightly between the sound board 2 and the posts 8so tightly that the bars will remain in place without other attachment and cannot be easily withdrawnexcellent results are obtained.

I have discovered that to get the full function and best results of a sound board, it must have strong support against the back pressure of the strings. The high string tension and the high back pressure of the strings on the bridges on the front of the sound board are necessary to produce the best tones and to efiicient transmission of vibrations from the strings to the sound board. Nevertheless, in conventional constructions the sound board reinforcing ribs afford relatively unstable support and the back pressure contact between the strings and the bridges gradually tends to become lessened as the crown in the sound board tends to become flattened. It is largely because of this that pianos generally tend to become out of tune, not only as a result of use and changes in string tension due to use and other causes, but also as a result of loss of crown in the sound board over a period of time regardless of use of the instrument.

By placing the support-tone bars 7 under high pressure, directly in back of, i. e., opposite the bridges and between the sound board and the back posts or other sturdy back parts of the piano case, the sound board is not only er" fectively supported as to its curvature or crown, but eflicient paths are provided through the bars 7 for the transmission of vibrations from the sound board 2 to the posts 8 and to other portions of the case which is thereby caused to vibrate and send out additional audible sound vibrations. Not only is the volume of the piano in creased, but it appears that many overtones or harmonies are more effectively amplified to audibility and the tone of the piano thereby improved.

The employment of the described bridge back pressure support-tone bars serves also to maintain the sound board in its proper, predetermined, crowned form in which it is best able to receive vibrations from the strings, and because of the very adequate support provided by the heavy posts 3 of the piano case, the predetermined crown of the sound board will be much more permanently maintained, probably for the life of the piano. Hence, tuning will be required much less frequently than with present standard rib-backed sounding board constructions.

The provision of the tone bar permits release of the sound board, heretofore bound by the ribs, to vibrate. By the reduction of the size and number of the reinforcing ribs, or by their total elimination as is permissible with my invention when the sound board is made of ply wood or in any other manner which avoids the need of the ribs for connecting together sections of the sound board or for other purposes, the deadening effect of the ribs on the sound board is eliminated and the latter enabled to more completely and freely respond to and reproduce the vibrations of the strings including many of the overtones. Hence, many tone qualities lost in present standard constructions will be made audible by thedescribed construction.

it is preferred that, as above indicated, the supporttone bars be placed in back of the center of the treble and bass bridges so that the maximum vibration transmitting efiect will be obtained, it being understood that 3 the bridges are the chief conductors of vibrations from the strings to the sound board. The employment of the tone bars nearer the ends of the treble bridge is not wholly necessary but it is preferred to support the crown of the sound board and when employed, said tone bars are located so as to be directly in back of the bridge for the reason already indicated. Furthermore, the bridges provide a backing which will prevent the tone bars from being forced through the relatively soft sound board.

In some pianos the back construction differs from that illustrated, especially in that the number of posts 8 may be other than the number here illustrated. In the event that the arrangement is such that a post 8 does not occur in alignment with the centers of the bridges 4 and 5 or in alignment with other bridge portions opposite to which support-tone bars are to be placed, special provision may be made for supporting the tone posts in back of the bridges. For example, as indicated in Figure 2, a cross member 9 represented in dotted lines, may be mounted on a pair of the posts 8 to provide a support which may be engaged by a tone bar 10 in back of the bridge but intermediate the posts 8. In some instances, especially with the smaller size pianos, posts such as the posts 8 may be found to be unnecessary for proper support of the piano case and therefore omitted by the piano manufacturers. In such an instance, suitable cross members may be applied to the back of the piano in any suitable manner to provide the desired seat for the tone bars.

For experimental purposes and to prove the effectiveness and practicality of the described construction, I purchased from a nationally known piano manufacturer one of its lowest grade pianos which has much poorer tone and less volume than its standard or better grade pianos. By inserting one tone bar between the sound board in back of about the middle of the bass bridge and the middle back post 8, another tone bar between the sound board in back of about the middle of the treble bridge and the central back post 8, and other tone bars between the sound board and the posts 8 in back of end portions of the treble bridge spaced from said middle part of the treble bridge and respectively on opposite sides thereof, I found that the tone of the piano was significantly improved and the volume increased, as near as I can judge, by more than 50 percent.

The tone and volume of this low grade piano, when improved as described, appears to be equal to the tone and volume of the best grade and highest priced larger sized pianos made by the same manufacturer. In the experimental construction just referred to, the sound board reinforcing ribs were permitted to remain in place because of the difiiculty of removing them without injury to the sound board despite which greatly improved tone and volume were attained. By removal of the rein-forcing ribs, or at least by reducing the size and number thereof, the sound board will be permitted much more freedom in responding to the vibrations transmitted thereto and further improvement in tone and volume will be experienced.

The tone and volume of the piano may be further improved by providing an effective resonating chamber. This may be provided by applying a suitable panel 11 to the back of the piano to form an echo chamber 12 be tween the sound board 2 and such back panel 11 and within the surrounding frame or case structure. The back panel 11 is preferably so secured to the piano case that the panel will clear the rear faces of the posts 8 so as to preserve the flexibility and vibrating capacity of said panel 11. The panel 11 may be a thin, flat wood panel of the same kind of wood as is employed in the sounding board 2 which, in some instances, consists of a panel of ply-wood. As indicated in Figure l, the back panel 11 is secured to the piano case by screws 13 spaced around the periphery of the panel, the panel being spaced from the posts 8 by means of edge spacer strips 14. When a assaoes 4 A V I back panel such as 11 is provided for forming an echo chamber as described, one or more sound openings, such as f openings indicated at 15, may advantageously be provided in the sound board, preferably but not necessarily, between the bridges 4 and 5 as illustrated and below the bass bridge 5. A single sound opening or more than two such openings may be provided if desired. The sound board of the piano is seated around its entire periphery on appropriate portions of the piano structure I is also the back panel 11 so that the echo tone chamber i2 is an air-tight compartment, except for the sound opening or openings 15, and said compartment acts as an echo chamber or resonator and increases the volume of vibrations and'deepens or mellows the tone of the piano.

The support-tone bars 8 in the experimental construction referred to were about of an inch in diameter and were made of straight grained spruce wood. However, these bars may be made of other kinds of wood and other kinds of materials, including metal. Spruce is, however, commonly although not exclusively used in sound boards and seems to be especially well suited to the transmission of sound vibrations.

The use of one or more tone bars located within the echo chamber in the manner above explained, not only improves the tone quality and increases the tone volume of the piano as above explained, but also provides many other advantages. For example, the tone bar provides very solid foundation for the bridge area of the sound board and supports the crowned or arched shape of the sound board, probably for the life of the piano. The tone bar compels the bridge which is the chief conductor of vibrations to the sound board, to transmit the vibrations with greater fidelity and vigor tothe sound board which is thereby caused to perform more fluently and efiiciently. Vibrations are effectively conducted by the tone bar from the bridge and sound board to all wood surfaces in the piano case and tone chamber, causing the latter to also act as a resonator to thereby contribute to the described beneficial results. By permitting elimination or at least reduction of the number and size of sound board reinforcing ribs, the tone bar, in effect, releases more sound board surface for vibration whereby the improved tone and increased volume are attained. Elimination of the reinforcing ribs, and even mere reduction in the number and size thereof, also affords the benefit of substantially reducing the cost of manufacturing the piano. Because of the improved action of the piano, the pianist can feel through the keys, more response when the hammer strikes the wires or strings and is thereby enabled to obtain better expression and shading.

To facilitate handling of the piano, hand-hold devices are suitably mounted in the back of the piano as indicated at 16, these devices preferably having their outer faces flush with the back of the back panel 11 and being recessed into the piano in order to give sufficient depth for an effective hand grip. These devices may be made of metal or other rigid material and serve also to protect the back panel 11 against destructive forces, especially against forces against the back or outside face of the panel. These hand grip devices also serve to eliminate, or at least partially eliminate, the need for special packing blocks between the back of the piano case and a shipping box in which the piano is transported.

The invention may be applied to both upright and grand pianos usually without any change in the normal construction of the piano, even to the extent that the conventional heavy reinforcing ribs 6 may remain in place although I prefer that they be either omitted or reduced in size and number. Reference in the following claims to the front and back of an upright piano should be interpreted respectively to refer to the top and bottom of horizontal or grand pianos.

Various changes in the described construction may made while retaining the principle thereof.

I claim:

1. A piano comprising a case having a sound board mounted therein, said sound board being crowned toward the front of the piano, bass and treble bridges secured to the front of said sound board and against which the strings of the piano exert pressure toward the back of the piano, a sturdy back structure rigid with said case and traversing the rear thereof in rearwardly spaced relation to said sound board, and a plurality of supporttone bars interposed between said back structure and said sound board, one of said bars being located approximately opposite to a central portion of said treble bridge and the others of said plurality of tone bars being located in spaced, surrounding relation to said one bar, said bars being respectively located opposite to portions of said treble and bass bridges and being under compression between said sound board and back structure.

2. A piano comprising a case having a sound board mounted therein, said sound board being crowned toward the front of the piano, bass and treble bridges secured to the front of said sound board and against which the strings of the piano exert pressure toward the back of the piano, a sturdy back structure rigid with said case and traversing the rear thereof in rearwardly spaced relation to said sound board, a support-tone bar interposed between said back structure and said sound board opposite to a central portion of said treble bridge, and a pair of support-tone bars respectively interposed between said back structure and said sound board opposite to portions of said treble bridge spaced from said firstmentioned support-tone bar on opposite sides thereof, and another support-tone bar spaced vertically from said first-mentioned tone bar and also interposed between said back structure and said sound board, said support-tone bars being under compression between said sound board and said back structure.

3. A piano comprising a case having a sound board mounted therein, said sound board being crowned toward the front of the piano, bass and treble bridges secured to the front of said sound board and against which the strings of the piano exert pressure toward the back of the piano, a sturdy back structure rigid with said case and traversing the rear thereof in rearwardly spaced relation to said sound board, a support-tone bar interposed between said back structure and said sound board opposite to a central portion of said treble bridge, a pair of support tone bars respectively interposed between said back structure and said sound board opposite to portions of said treble bridge spaced from said first-mentioned supporttone bar on opposite sides thereof, another support tone bar spaced vertically from said first mentioned tone bar and interposed between said sound board and said back structure, said support-tone bars being under compression between said sound board and said back structure, and

a flat back panel spaced rearwardly from said back structure and seated on the piano case around said back structure so as to cooperate with said sound board and portions of said case to form an echo chamber.

4. A piano comprising a case having a sound board mounted therein, said sound board being crowned toward the front of the piano, bass and treble bridges secured to the front of said sound board and against which the strings of the piano exert pressure toward the back of the piano, said case having a substantially rigid back structure comprising a central post extending vertically across the back of the piano approximately midway of the width of the case, and a pair of substantially rigid, vertical posts which extend vertically across the back of the piano in spaced relation to said central post and respectively on opposite sides thereof, a pair of vertically separated support-tone bars interposed between vertically spaced portions of said sound board and said central post, one of the bars of said pair of support-tone bars being located opposite to a portion of said treble bridge, and a pair of support-tone bars respectively interposed between said sound board and said pair of posts of the piano case, said support-tone bars being under compression and thereby held in place between the sound board and said posts as aforesaid.

5. A piano comprising a case having a crowned sound board mounted therein, bass and treble bridges secured to the convex side of said sound board and against which the strings of the piano exert pressure which tends to flatten the crown of the sound board, said case having a sturdy frame structure opposite the concave side of said sound board in spaced relation thereto, and a plurality of support-tone bars interposed under compression between said sturdy frame structure and the concave side of said sound board, there being two of said bars respectively located opposite to portions of said treble and bass bridges to transmit the vibrations of said sound board from its most strongly vibrated portions to said frame structure and case and to support the crown in said sound board against the pressure of said strings, and other of said plurality of bars being located in spaced relation to said two bars and serving to assist the latter to support the crown in said sound board against the pressure exerted thereon by the strings of the piano.

References Cited in the file of this patent UNITED STATES PATENTS 1,218,019 Thomas Mar. 6, 1917 1,331,572 Lutz Feb. 24, 1920 FOREIGN PATENTS 1,409 Great Britain June 9, 1890 40,997 Austria Feb. 25, 1910 

